Software-defined networking (SDN) is an emerging network architecture that promises to simplify network management, improve network resource utilization, and boost evolution and innovation in traditional networks. The SDN allows the abstraction and centralized management of the lower-level network functionalities by decoupling the network logic from the data forwarding devices into the logically centralized distributed controllers. However, this separation introduces new scalability and performance challenges in large-scale networks of dynamic traffic and topology conditions. Many research studies have represented that centralization and maintaining the global network visibility over the distributed SDN controller introduce scalability concern. This paper surveys the state-of-the-art proposed techniques toward minimizing the control to data planes communication overhead and controllers' consistency traffic to enhance the OpenFlow-SDN scalability in the context of logically centralized distributed SDN control plane architecture. The survey mainly focuses on four issues, including logically centralized visibility, link-state discovery, flow rules placement, and controllers' load balancing. In addition, this paper discusses each issue and presents an updated and detailed study of existing solutions and limitations in enhancing the OpenFlow-SDN scalability and performance. Moreover, it outlines the potential challenges that need to be addressed further in obtaining adaptive and scalable OpenFlow-SDN flow control.

The pipeline leakage problem is a very challenging and critical issue. Solving this problem will save the nation a lot of money, resources and more importantly, it will save the environment. This paper discusses the state of the art of leak detection systems (LDSs) and data fusion approaches that are applicable to pipeline monitoring. A comparison of LDSs is performed based on well-defined criteria. We have classified and critically reviewed these techniques. A thorough analysis and comparison of all the recent works have been provided.

Many important and critical applications use Wireless Sensor/Actuator Networks (WSAN). These applications are spanning widely that range in several environments, including industrial, commercial and residential. Most of these applications need a certain level of real-time communication in addition to reliable data delivery service. Data Distribution Service (DDS) is a known standard for supporting real-time distributed systems based on the publish/subscribe model. The DDS specification offers two disparate Quality-of-Service (QoS) levels of data reliability, namely: best-effort and fully-reliable. TinyDDS is a lightweight and partial porting of DDS middleware to sensor-based platforms, specifically for platforms with limited resources. However, TinyDDS in its current form lacks the reliability support for data delivery. In this paper, we extended the DDS data reliability service and integrated it into TinyDDS, which resulted in Reliable TinyDDS (RTDDS). Moreover, we provide a prototype and comprehensive performance evaluation of the reliability functions taking into account: number of hops, number of publishers, and several other network parameters. The achieved results indicate that reliable data delivery in real-time for WSAN is possible with optimized system parameters, such as retransmission time-out value of 400ms and number of hops not exceeding 10 for an end-to-end delay ranging from 10s to 100s of milliseconds.

A Mobile Ad-hoc NETwork (MANET) is an infrastructureless network consisting of self-configuring mobile nodes connected by wireless links. Nodes rely on each other to store and forward packets. Most of the proposed MANET protocols assume cooperative and friendly network context, and do not address security issues. Furthermore, MANETs are highly vulnerable for passive and active attacks because of their open medium, rapidly changing topology, lack of centralized monitoring. Encryption and authentication solutions, which are considered as the first line of defense, are not sufficient to protect MANETs from packet dropping attacks. Most of the current Intrusion Detection Systems (IDSs) for MANETS rely on the Watchdog technique. In this research we study the behavior of this technique and propose a novel mechanism, named: Adaptive ACKnowledgment (AACK), for solving two significant problems: the limited transmission power and receiver collision. This mechanism is an enhancement to the TWOACK scheme where its detection overhead is reduced while the detection efficiency is increased. NS2 is used to simulate and evaluate the proposed scheme and compare it against the TWOACK and Watchdog methods. The obtained results show that the new AACK scheme outperforms both of the TWOACK and Watchdog methods in terms of network packet delivery ratio and routing overhead.